To do it, they had to figure out how to measure the stretching and squeezing of spacetime by impossibly tiny amounts – much smaller than a single atom.

In 1972, Weiss, a physicist at the Massachusetts Institute of Technology (MIT) developed the original idea to do it using laser interferometry – an instrument that can measure minute changes in length using a beam of light.

He realised that the two arms of an interferometer, placed at right angles to one another to make an ‘L’ shape, would be perfect for detecting a passing gravitational wave since the warping would squeeze one arm and stretch the other. The relative change in length of each arm would then show up as a signal.

In 1975, Weiss teamed up with Kip Thorne (the rockstar physicist who developed the ideas behind the movie Interstellar) to try to realise his idea.

Thorne, a theoretical physicist at the California Institute of Technology (Caltech), had already been using Einstein’s theory to work out how extreme events, such as colliding black holes or neutron stars, would generate gravitational waves.

Thorne worked out what the signals would look like on Weiss’s interferometer. It was this work that told physicists how to calculate the masses of two colliding black holes, once the Laser Interferometer Gravitational-wave Observatory, or LIGO, eventually detected a collision.

Over the decades the LIGO project grew. It was a group of around 40 researchers in 1994 when Barry Barish, the third recipient of this year’s prize, began leading the project. He helped it grow further and develop into the massive international collaboration, with more than 1000 researchers, that finally succeeded in detecting the waves in 2015.

The pioneers of gravitational-wave astronomy had their work cut out for them, as most of the physics community didn’t think the idea could work, explains Yuri Levin, a physicist at Monash University in Melbourne, Australia who works on the LIGO.

“These guys are amazing. They started out, 40 or 50 years ago, thinking about this, and it took all this time to convince people,” he says.